Walnut Cake with Chocolate Mousse

Preheat the oven to moderate temperature (170°F)

Butter two 22cm-diameter tart pans and dust with flour

Beat the yolks until thick and pale

Add the rum, coffee, and chopped walnuts, beating well

Place the mixture in a large bowl

Beat the egg whites until stiff and shiny, but not too dry

Mix in one-fourth of the beaten egg whites to the walnut mixture, then add the remaining egg whites, mixing carefully

Divide the dough between the two tart pans, using a spatula to distribute evenly

Bake for 30 minutes and let cool in the pans

Prepare the chocolate mousse: mix the chocolate with coffee

Melt the sugar and water over low heat

Add the melted mixture to the chocolate mixture, beating constantly until smooth. Reserve

Beat the egg whites until stiff

Add the remaining sugar and continue beating until stiff peaks form

Add the yolks and vanilla extract to the chocolate mixture, beating well and scraping down the sides with a spatula

Mix in the whipped egg whites carefully

Cover with aluminum foil and refrigerate until firm and spreadable

Spread a layer of 2.5cm of mousse over one cake and top with the other

Spread the remaining mousse on top and smooth with a spatula

Garnish with walnut halves.